"Civil servant language" is another instance of Americans using a noun where an adjective belongs.
It is an unkind (poco gentile) phrase meaning that the language is so obfuscated (offuscato) and impersonalized that it has become almost meaningless (senza significato) and inscrutable (impenetrabile).
EDIT: Because it has this meaning, it would rarely be used to seriously describe the language of public administration, at least in the USA. I would infer from Rob's comments that in the UK, this phrase is rarely used, so it probably would not be offensive there. I think most civil servants in the USA would chuckle rather than be offended, because they would agree that the language is inscrutable.
EXAMPLE: A civil servant never says "I am on business travel." He says "I am (on) TDY." He says it "tee dee why" (TDY = temporary duty) Non civil servants do not understand this.